Method of producing titanium alloys



Patented Sept. 19, 1950' UNITED STATES. PATENT .OFFICE METHOD OF PRODUCING TITANIUM ALLOYS William J. mu, Niagara Falls, N1.

N Drawing. Application February 17,1945.

Serial No. 578,540 r 1 Claims.

1 This invention relates to metallurgical processes and more particularly to' a method of producing alloys consisting principally of titanium.

tling,oxide, nitride and hydride compounds and cold malleable which method consists in causing a, halide compound of titanium, such as'the tetra chloride, to chemically react with an alkaline earth metal, such as magnesium, at an elevated temperature below the boiling point of the alkaline earth metal and in an inert atmosphere at a pressure approximating normal or atmospheric pressures. In the practice of this method the titanium tetra chloride in its liquid anhydrous phase substantially free of precipitated titaniumoxide compounds, is fed relativel slowly into a molten alkaline earth metal bath, preferably.

magnesium, heated to temperatures not in excess of the boiling point, while maintaining-an inert atmosphere, preferably .argon, atatmospheric pressure in a reaction chamber enclosing the'bath and contacting tetra chloride. Bymeans or this 3-5 reaction, titanium metal substantially free; of oxide, nitride and hydride compounds-is prepared, which on being separated from the contaminatins excess magnesium and the magnesiumchloride reaction productassociated therewith in'the manner disclosed in thepatent, -may-=-be-consoli-' dated and sintered into a coherentmetal body of high hot and cold ductility.

z I A'further object is to provide alloys consistin I mainly of titanium and in minor partv of a metal whose chloride compound is-reducible by an alkaline earth metal, particularly magnesium, in accordance with the method of my said patent. A'still further object is to provide a new type getter material for electron and gaseous conduction discharge devices.

Other objects will be apparent asthe invention is hereinafter more fully disclosed.

In accordance with the above objects I have discovered that liquid titanium tetrachloride possesses the unique property'of dissolving other metal chloride compounds to form therewith, by-

reaction with any water present in the other metal chloride, anhydrous and oxide-free chloride solutions which are suitable for reduction in accordance with the invention 01 my above noted patent to form titanium alloys oi the dissolved other metal chloride.

The solvent action of. titanium tetrachloride for i other metal chlorides varies widely, as one skilled in the art would expect, depending upon the particular other metal chloride involved and upon the temperature of the solution. It 'is'extr'emely difiicult to: produce anhydrous and oxygen-free 'metal"chlorides-'forsolution .titanium.-.tetra chlorideandmostmetal ehlorides'contain either 1 2 oxygen held in the-format oxide, mnemonic-or:

combination 5- Surface 'Tillailiumf tetlf80hlO11d;1I0W8Vel3j%3fiEyfiD- 1. tive with water forming-titanium-oxide and liber- I water held as water orscrystallizatiomgwater-oi ating hydrogen chloride. This reaction is so strong that upon-dissolving any metal chloride in titanium tetrachloride all water present-in the metal chloride is convertedto titanium'oxide and is precipitated; out ofsolntion to ether with any I. oxide or oiz'ide'compounds. "precipitated The object of the present invention is to -provide a method of forming alloys consisting principally of titanium by the practice of the general method disclosed in my said patent.

Another object is to provide a method of forming anhydrous metal chlorides.

Still another object is to provide a method of obtaining liquid mixtures consisting mainly of titanium tetra chloride and in minor part or another metal chloride which mixture is substantially free of metal oxides or contained water, for reduction in accordance with the invention oi my said patent.

"titanium: oxidgusually TiOz, can :readilybearev moved by filtratlom 'decantation orcentrifuging from the solution. 'Toe'ilect filtration it is often necessary to heat the solution, sometimes toes high as its boiling point, to obtain -a filter-able liquid phase. The-entire process of dissolving the metal chloride in the titanium tetra, chloride. heating and filtering the same, must be performed in an atmosphere substantially free of water vapor. Pure dry air. is a suitable atmosphere but other dry gases can also be used.

This unique property of'titanium tetrachloride of dissolving other metal'chlorides and or freeing the other metal chlorides, in the process of 618- solving, of contained water, may be adapted to a plurality ofidiflerent useful -purpose s.- It prometal form thereby to obtain one of a plurality.

of possible alloys having titanium as a base.

In the preparation of anhydrous metal clilcrides in accordance with the present invention several alternative methods are available. One

method involves the use of a suiilcient excess of the solvent, titanium tetrachloride, to form at some temperature below the boiling point of the titanium tetrachloride a highly concentrated solution of the metal chloride which, after filtering, decanting or centrifuging, is heated under reduced pressures to temperatures effective to distil of! substantially all of the titanium tetrachloride leaving the anhydrous metal chloride behind as a residue. Another method'is one wherein the amount of titanium tetrachloride employed is calculated with respect to the solubility of the metal chloride therein at temperatures closely approximating the boiling point of the solvent tetrachloride to produce a saturated solution which, after filtering while hot, is-cooled to very low temperatures to eflect precipitation of the dissolved metal chloride. After filtering 01!, de-

a minor alloy constituent in the titanium as will,

on reduction with the titanium tetra chloride,

provide the desired amount of the metal as an alloy constituent in the titanium. The specific amounts of metal chloride employed may vary widely without essential departure from the present invention, depending upon the metal chloride involved, and the type of alloy involved.

A large number of alloys are possible of production in accordance with the present invention. Practically all metal chlorides have been found to have some solubility intitanium tetra chloride. Also practically all metal chlorides except the alkali metal chlorides arereducible by alkaline earth metals and magnesium in accordance with the invention of my said patent. There is, accordingly, a wide choice of alloy compositions producible in accordance with the present invention.

As a specific embodiment of the invention, but not as a limitation thereof, the preparation of a typical example of an alloy included in the group of alloys consisting principally of titanium and in minor part of at least one of the other so-called rare metals, will bedescribed. This group of alloys offers wide possibilities for adaptation as getter agents in the clean-up of gases 4 in all types of evacuated and gas-nlledelectrical devices, such as lamps, radio tubes, gaseous conduction discharge devices, electron discharge devices, etc. In such devices it is customary to employ such a getter agent to clean up residual atmospheric gases, such as oxygen, nitrogen and hydrogen, within thedevice after sealing the same from the atmosphere. The highly oxidizable socalled "rare metals have heretofore been found highly suitable for such clean-up purposes due to their low vapor pressure and to their universal property of forming highly stable compounds with oxygen, nitrogen and hydrogen. The major difflculty, heretofore, has been'to prepare thesemetals in a, metallic form sufficiently free of these compounds to utilize these properties. By the practice of the present invention titanium alloys of one or more of these metals may be prepared in a high state of purity admirably well suited for use as gas clean-up or getter agents in said devices.

By the term rare metals" is meant those metals of the zirconium, vanadium and chromium groups, 1. e., Zr, Hf, Th, V, .Cb, Ta, Cr and U.

The chloride compounds of each of these metals are well'known and various methods have heretofore been disclosed in the art for producing the same. The particular method of producing these metal chlorides in their substantially anhydrous oxide-free condition, per se, forms no part of the present invention, except insofar as that method is improved or modified by the pract ce the method of the present invention adap the forming of oxide-free, anhydrous metal chlorides as hereinabove disclosed.

0f the large number of possible alloys of titanium with one or more ofthe rare metals, the type of alloy most suitable for use as a gas cleanup or getter agent is the alloy with one or more of the metals of ,the vanadium group (V, Cb and Ta). An alloy of titanium and one of the metals of the vanadium group inherently possesses high chemical activity towards each of the gases oxygen, nitrogen and hydrogen. In addition to this property, these alloys inherently possess a remarkably high creep strength and resistance to deformation or stiffness even at relatively high temperatures. This property is particularly valuable in connection with the use and adaptation of these alloys as lead-in and support wires in various types of electrical discharge and electronic devices, such as gaseous condensation discharge devices, radio tubes, and the like.

- Of the vanadium group metals, I prefer to employ tantalum rather than columbium or vanadium, for the reason that this metal in amounts ranging from'lo to 25% imparts to the oxide-, nitrideand hydride-free titanium relatively high cold workability thereby providing for ready conversion of the alloy into relatively thin strip or small diameter wire which facilities the utilization of the material in the electrical device. Various titanium-tantalum alloys may be formed and all of them are utilizable as getter agents, as even a small percentage of Ta in the Ti markedly increases the hydrogen reactivity of the titanium. The alloy I have found most suitable as a getter agent, however, is one that contains about 20% Ta. This alloy is highly cold ductile and may be easilycold worked down into relatively thin sectioned strip or small diameter wire. The major advantage of such thin sectioned strip or small diameter wire is that such products may be more economically and easily mounted within the radio tube or other such device and the amount thereof employed may be more easily regulated. Columbium and vanadium alloys of titanium, however, possess good cold working properties.

In the preparation of the preferred titaniumtantalum alloy of the present invention, I follow the general practice outlined above with the following added details:

Tantalum chloride (TaCls) prepared by any heretofore proposed method which is as near anhydrous and. oxide-free as possible to obtain by said prior art method, is dissolved in titanium tetrachloride under a moisture free atmosphere,-

the solution is filtered, decanted or centrifuged, free of insolubles and oxides, and is reduced precisely as described in my said patent, using molten magnesium as a reducing agent. The reduced metal is recovered and converted to coherent substantially pure form, 1. e., free of magnesium and magnesium chloride, by the general procedure outlined in my said patent, and the resultant coherent Ti-Ta alloy, then is cold worked down to thin section strip or small diameter wire, as may be preferred, utilizing equipment and methods well known in the art. The resultant strip or wire product, after surface cleaning, is then out up into small pieces for use as getter material in the usual manner in the evacuated or gas-filled electrical devices mentioned above. No particular difiiculty attends the use and adaptation of this new getter material in the art. It may be welded or mechanically secured in position in the device and being metallic it may be readily heated by induction heating to the reaction temperature which is in the neighborhood of a bright red heat.

In the manufacture of this alloy, I have found that at 25 C., titanium tetrachloride will dissolve about 14 to 15% TB-Cls while at about the boiling point of T1014 (136.4 C.) about 40% TaCls will dissolve in rich. These figures are based on weight dissolved per unit weight of solvent.

The solubility of CbCls in TiCh is much lower being in the neighborhood of 24% at 25 C. and 2% at 136.4 C. Zirconium chloride, on the other hand, has a greater solubility in 'IiCli, being in the neighborhood of ZrCl4 at about 25 C.

I prefer to employ, in the forming of about a 20% Ta alloy of titanium, a solution that contains in the neighborhood of 11.5 grams TaCls per hundred. This solution is freely liquid at atmospheric temperatures and is readily filterable free of insoluble materials present therein, and upon reduction by molten magnesium, in accordance with the method of my said patent, yields consistently about a 20% Ta alloy.

In the reduction of anhydrous solutions of one or more of the rare metal chlorides in titanium tetra chloride by magnesium in accordance with the method of my said prior patent, the relative proportions of the titanium chloride and the rare metal chlorides dissolved therein are adjusted to approximate that providing on reduction the approximate desired percentage of the associated metal in the titanium metal. In some instances this requires the incorporation in the titanium tetrachloride of a larger amount of the dissolving metal chloride than normally may be held in solution at any temperature below the boiling point of the titanium tetrachloride, and may require the use of a suspension or slurry consisting of titanium tetrachloride saturated at the temperature of heating with metal chloride and containing suspended undissolved anhydrous metal chloride. Some suspensions or slurries, for example, are readily produced by dissolving the desired amount of metal chloride in a sumcient volume of titanium tetrachloride to eifect complete solution of the same, filtering the solution to re-.. move titanium dioxide formed as aresult of reac- 1 tion of the titanium tetrachloride with water present in the metal chloride, and then evaporating oil the excess titanium tetrachloride in any convenient manner. as by vacuum distillation.

By the use of solutions of various metal chlorides in titanium tetrachloride reduced to metal-.7;

'lic form by magnesium in accordance with the invention of my above noted patent, I have been able to produce a large number of different titanium base alloys which, being substantially free of the embrittling constituents oxygen, nitrogen, carbon and silicon, are usually ductile and workable either when hot or when cold. The

physical, chemical and metallurgical properties of these alloys have not as yet been fully deter mined. Many of these alloys appear promising as corrosion resistant alloys; others appear promising for special fields of use, such as electrode and getter materials in electronic devices; still others and in minor part of one or a plurality of associated rare metal alloy constituents. Various other highly reactive metals utilizable as getter materials may be substituted for Ta, in part or in whole, in the specific example given above without essential departure therefrom, such as one or more of the rare earth metals, vanadium, columbium, zirconium, hafnium, thorium. uranium, etc. The essential step involved in theforming of any solution of metal chlorides in titanium tetrachloride is to separate the solution free of precipitated titanium oxide (T102) prior to reducing the solution in accordance with the invention of my said co-pending application. Titanium tetrachloride, being a liquid at atmospheric temperatures and not boiling at temperatures below about 136.4 C., presents no great difliculties as a solvent for other metal chlorides except that during the production of the solution, the, filtering of the same, and the introduction ofli'e solutiem the alloys. The method'of preparing these alloys 7 several specific examples or the same, it is believed apparent that the invention is adapted for wide modification without essential departure therefrom and all such modifications and adaptations are contemplated as may fall within the scope of the following claims.

What I claim is:

1. The method of forming a completely dehydrated metal chloride which comprises dissolving a substantially dehydrated metal chloride in liquid titanium tetrachloride, separating the liquid and solid phases obtained thereby, and separatin the titanium tetrachloride of the liquid phase from the metal chloride contained therein.

2. The method of forming a completely dehydrated metal chloride which comprises dissolving a substantially dehydrated metal chloride in liquid titanium tetrachloride, separating the liquid phase chlorides from the solid phase materials present therein, and distilling off the titanium tetrachloride content of the liquid phase to recover the metal chloride content dissolved therein.

3. The method of forming anhydrous tantalum chloride which comprises dissolving substantially dehydrated tantalum chloride in liquid titanium tetrachloride, separating the liquid phase chlorides from the solid phase materials present therein, and heating the liquid phase chlorides to a temperature effective to vaporiz the titanium tetrachloride only.

4. The method of forming anhydrous metal chlorides which comprises suspending a substantially anhydrous metal chloride in liquid titanium tetrachloride, heating the suspension to a temperature not in excess of the boiling point of the titanium tetrachloride to obtain a saturated solutlon of th: suspended chloride therein, filtering the solution while hot to separate the solution from the insoluble materials contained therein, cooling the solution to precipitate therefrom the said other metal chloride in excess of the solubility limit at said lower temperature, and separating the liquid and solid phase chlorides resulting.

5. The method of producing titanium-base alloys substantially free of embrittiing oxide, nitride and hydride compounds which comprises forming a liquidphase mixture of metal chlorides consisting predominantly of titanium tetrachloride and in minor part of at least one other metal chloride which is soluble in the liquid phase titanium tetrachloride. filtering the same to remove oxygen-containing insolubles therefrom and reducing the filtered mixture to metal powder form by reacting the same with molten magnesium under an inert gas maintained at atmospheric pressure, separating the metal powders obtained from the excess magnesium and from the magnesium chloride product of the reduction reaction, and compacting and sintering the recovered metal powders to coherent metal in an inert atmosphere.

6. The method of claim 5, wherein said other metal consists of a metal of the rare metal group.

7. The method of claim 5, wherein said other metal consists of tantalum.

WILLIAM J. KROLL.

REFERENCES CITED "he following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date I 1,646,734 Marden Oct. 25, 1927 1,671,213 Van Arkel et al May 29, 1928 1,709,781 De Boer et a1 Apr. 16, 1929 2,205,854 Kroll June 25, 1940 2,230,538 Jenness et a1. Feb. 4, 1941 2,344,319 Meister Mar. 14, 1944 FOREIGN PATENTS Number Country Date 718,822 Germany Feb. 26, 1942 OTHER REFERENCES Chemical Abstracts," vol. 37 (1943), page 1694,

Chapters in the Chemistry of Less Familiar Elements, vol. 2, 1939. by Hopkins. chapter 12, page 5. 

5. THE METHOD OF PRODUCING TITANIUM-BASE ALLOYS SUBSTANTIALLY FREE OF EMBRITTLING OXIDE, NITRIDE AND HYDRIDE COMPOUNDS WHICH COMPRISES FORMING A LIQUID PHASE MIXTURE OF METAL CHLORIDES CONSISTING PREDOMINANTLY OF TITANIUM TETRACHLORIDE AND IN MINOR PART OF AT LEAST ONE OTHER METAL CHLORIDE WHICH IS SOLUBLE IN THE LIQUID PHASE TITANIUM TETRACHLORIDE, FILTERING THE SAME TO REMOVE OXYGEN-CONTAINING SOLUBLES THEREFROM AND REDUCING THE FILTERED MIXTURE TO METAL POWDER FORM BY REACTING THE SAME WITH MOLTEN MAGNESIUM UNDER AN INERT GAIN MAINTAINED AT ATMOSPHERIC PRESSURE, SEPARATING THE METAL POWDERS OBTAINED FROM THE EXCESS MAGNESIUM AND FROM THE MAGNESIUM CHLORIDE PRODUCT OF THE REDUCTION REACTION, AND COMPACTING AND SINTERING THE RECOVERED METAL POWDERS TO COHERENT METAL IN AN INERT ATMOSPHERE. 